Tuberculosis (TB) is the most common cause of death among people living with HIV. Diagnosing latent tuberculosis infection (LTBI) among HIV-infected patients is challenging, as the most commonly used test, the tuberculin skin test (TST), is out-dated, has poor sensitivity in HIV-infected and BCG vaccinated populations, and is operationally difficult to administer. The World Health Organization currently recommends that in regions where the TST can be implemented to detect LTBI, provision of preventive therapy is recommended only for HIV-infected patients with a positive TST. A new blood assay, Quantiferon TB Gold In-Tube (QGIT) test, has been recently approved by the US FDA for detecting LTBI, however relatively few published studies have evaluated this assay in HIV-infected patients and little information exists about the routine use of QGIT, i.e. test performance under routine clinical care conditions and optimal operationalization of this blood test. We propose a cluster randomized trial (CRT) to compare QGIT performance in HIV-infected persons attending public HIV clinics in Rio de Janeiro, Brazil with routine TST, and to determine if QGIT more quickly identifies HIV-infected patients who are latently infected and leads to faster initiation of TB preventive therapy. We will link QGIT testing with routine CD4 monitoring which will eliminate the burden of the routine clinic staff and minimally interfere with routine blood draws. Delays in TST and provision of isoniazid preventive therapy in Rio de Janeiro are extremely long, and risk of TB disease is quite high among HIV-infected patients waiting for a TST, thus a better strategy is needed. The specific aims of the study are 1) to compare the impact of linking QGIT with CD4 blood collection and the current standard of care process of TST in HIV clinics in Rio de Janeiro, Brazil on operational metrics, 2) to compare cost-effectiveness of implementing QGIT versus standard practice of TST, and 3) to explore attitudinal and operational factors influencing successful implementation of QGIT. Our primary focus on linking QGIT with routine CD4 blood draws is innovative and logical given the parameters of the test. These findings, in addition to conducting a structured process evaluation of the implementation of the intervention and determining the cost effectiveness of QGIT compared to TST will provide the best evidence to date comparing these two tests in an operational setting in a developing country, and guide dissemination and implementation of this strategy throughout Brazil and other regions where TST is ineffective at diagnosing latent infection in HIV- infected patients.